Variance map of an image is calculated by taking a square window of a set size around a center pixel, and calculating the variance of the values of the pixels.

Census Transform is a form of non-parametric local transform (i.e. relies on the relative ordering of local intensity values, and not on the intensity values themselves) used in image processing to map the intensity values of the pixels within a square window to a bit string, thereby capturing the image structure [1]. The centre pixel’s intensity value is replaced by the bit string composed of set of boolean comparisons such that in a square window, moving left to right,